Halogenated anesthetics inhibit Pseudomonas aeruginosa growth in culture conditions reproducing the alveolar environment

We assessed the effects of halogenated anesthetics on Pseudomonas aeruginosa growth in a liquid nutrient broth. Sterile Petri dishes (3.5-cm diameter) were filled with a 1-mL suspension of a Pseudomonas aeruginosa strain and incubated at 37 degrees C. Exposure of bacterial plates to halothane, isoflurane, and enflurane administered at 1 and 2 minimum alveolar anesthetic concentration (MAC) were studied for different exposure times (1, 2, 3, and 4 h) using an airtight chamber. For each time, a control point was obtained. Serial dilutions and agar plates were made, and developed colonies were counted. A significant decrease in bacterial growth was observed from the second hour of exposure to every halogenated anesthetic. For long periods of exposure (3 and 4 h), bacterial growth was significantly reduced in the plates exposed to 2 MAC compared with 1 MAC. The maximal inhibition was observed after a 4-h exposure at 2 MAC and reached 60%, 49%, and 42% for halothane, isoflurane, and enflurane, respectively. We conclude that a decrease in Pseudomonas aeruginosa growth is observed after exposure to halogenated anesthetics, but whether this inhibition is clinically important remains to be demonstrated. Implications: Bacterial pneumonia is a major source of morbidity after general anesthesia. We measured the effects of volatile anesthetics on the growth of Pseudomonas aeruginosa, one of the pathogens most often isolated in hospital acquired pneumonia. The experiments were performed in vitro in culture conditions reproducing those observed in the alveolar space. Volatile anesthetics inhibited the growth of these bacteria, but the clinical significance of this fact remains to be determined.